For example, a nail driver generally uses compressed air as a drive source, and a large striking can be exerted by reciprocating a piston by compressed air. In contrast thereto, there is provided a nail driver for driving driven pieces, such as nails or the like, by reciprocating a driver (striking rod) for striking by using a an electric motor as a drive source. In the case of the driving tool of the electric type, measures for achieving a large striking force have been provided in the art. These various measures are described in, for example, Patent References 1 through 3 shown below. A technology disclosed in Patent Reference 1 is constructed for providing a striking force to a driver by bringing a drive wheel rotated by an electric motor into contact with a driver or separating the drive wheel therefrom by an electromagnetic actuator in order to clamp the driver between support rollers.
Further, a technology disclosed in Patent Reference 2 is constructed for providing a striking force to a driver by clamping the driver between drive wheels rotated by an electric motor, by bringing an idler wheel into contact with the driver or separating the idler wheel from the driver by a toggle mechanism.
Further, a technology disclosed in Patent Reference 3 is constructed for providing a large striking force resulting from a large friction resistance obtained by providing a plurality of V-shaped groove portions on a side of a reciprocating driver and, on the other hand, by providing a projected streak having a V-shaped cross section, which meshes with the V groove on the side of the driver, on a circumferential face of a drive wheel, in order to increase a contact area of the drive wheel with the driver.    Patent Reference 1: JP-A-2006-142392    Patent Reference 2: JP-A-6-179178    Patent Reference 3: US Patent Publication No. 2005/0218183